1. Field of the Invention
The present invention generally relates to AC switches, that is, switches intended to control a load powered by an AC voltage or current and, more specifically, an interface circuit between such a switch and a digital control circuit.
The present invention more specifically applies to the case where information about the AC switch or the load is sent back to the digital control circuit.
2. Discussion of the Related Art
Current solutions for transmitting control signals from a digital circuit to an AC switch, and for transmitting to the digital control circuit information about the load controlled by this switch or about the state of this switch, require at least two communication links with the digital circuit.
Increasingly, a same circuit integrates one or several AC switches connectable to a high-voltage load (for example, powered by the AC electric power system voltage of more than one hundred volts) and their control circuits (“control parts”) capable of receiving low-voltage signals (for example, from a few volts to a few tens of volts) originating, for example, from a digital control circuit.
It would be desirable to be able to share the same connection to exchange control and information signals between an AC switch and its control circuit.
U.S. Pat. No. 6,476,709 describes data transmission over an AC power supply line of a load to be cyclically supplied, comprising the organizing of a division of the AC supply voltage according to a coding of the data to be transmitted and outside cyclic load supply periods.